Description of problem:

---
$ cat <<EOF >Makefile
foo:    CFLAGS+=a
EOF
$ touch foo.c
$ CFLAGS=a make foo
cc a a    foo.c   -o foo
make: expand.c:489: allocated_variable_append: Assertion
`current_variable_set_list->next != 0' failed.
---

(e.g. seen when building valgrind)


This is perhaps an upstream bug but because RHL ships a historic version of
make, I do not know if it happens with the recent 3.80 version also.


Version-Release number of selected component (if applicable):

make-3.79.1-17


How reproducible:
100%